Genetically engineered mouse models of autosomal recessive polycystic kidney disease (ARPKD) provide model systems to study cyst development in kidney, liver and pancreas. This work has led to the surprising observation that apical cilia play a pivotal role in the pathogenesis of ARPKD. However, there is a lack of information concerning the physiological mechanisms that result in cyst formation. This Cellular Physiology Core will provide a comprehensive facility to perform state-of-the-art physiological experiments in cells and tissues from mouse models of ARPKD. One unique aspect of this Core is the breadth of experimental tools and resources that have been amassed to attack specific problems and questions. The other unique aspect of this Core is the ability to isolate renal tubules and ducts, to produce primary and immortalized cell lines, and to apply experimental procedures and techniques that maximize the physiological information that can be obtained from freshly isolated tissues or cultured cells. The Physiology Core is capable of assessing alterations in the rate of electrolyte and water transport in isolated perfused renal tubules and ductal epithelium and in cultured cells grown on permeable supports. In addition, this Core utilizes advanced fluorescence imaging and multi-photon confocal microscopy to study transporter and channel function, transport rates, and regulation of cytosolic calcium, pH, sodium and chloride. Furthermore, using 2-photon microscopy, this Core now has the ability to visualize and resolve subcellular domains in living cells providing novel and detailed information on ion concentrations in cellular microdomains. For instance, recent work in the Core laboratory has revealed elevated subapical membrane calcium levels in an ARPKD collecting duct cell model. Other capabilities include patch clamp analysis, advanced immunofluorescence techniques, and evaluation of paracrine and autocrine signaling using a biosensor approach. Mice that are generated by the Engineered Mouse Core will be used to obtain fresh tissue and to establish primary and immortalized cell lines. The ability to compare the results obtained in freshly isolated tissues versus primary and immortalized cell lines is one of the major strengths of this Core facility. Overall the Cellular Physiology Core will provide the RPKDCC Investigators with a wide range of tools and expertise to define the physiological mechanisms that are involved in the pathogenesis of ARPKD in renal tubules and epithelial cells.